CYTO-TOXICITY AS AN INDICATOR FOR TRANSPORT MECHANISM - EVIDENCE THAT MURINE BONE-MARROW PROGENITOR CELLS LACK A HIGH-AFFINITY LEUCINE CARRIER THAT TRANSPORTS MELPHALAN IN MURINE L1210 LEUKEMIA-CELLS
Cytotoxicity of melphalan to murine L1210 leukemia cells was reduced to a limiting maximum value of 50% by 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH), indicating that cytotoxicity is partially dependent on drug uptake by system L. L-Leucine, but not .alpha.-aminoisobutyric acid (AIB), completely reduced the remaining 50% of drug cytotoxicity. These results contrast with those obtained with a sensitive host tissue, the bone marrow progenitor cells of the white cell series (CFU-C), in that a high-affinity leucine transport system corresponding to system L was not identified.